Revolution itself, that their country should remain aloof from European affairs and offer an example of democracy and peace to the rest of the world. But the United States had become a great power by virtue of its prodigious economic growth since the Civil War; now many thought it ought to begin to act like one. In World War I, and again in World War II, American industrial might and military technology proved decisive. However, the debacle of Vietnam, set in the morass of the Cold War, shook America's belief in its "victory culture" and "manifest destiny," a malaise that would not pass for 20 years. Lasting but 40 days, the Gulf War was easily won by the U.S.-led coalition at only slight material and human cost, but its sophisticated weapons - spearheaded by the American F-15 fighters - caused heavy damage to Iraq's military and economic infrastructure. With the declining power (and subsequent collapse in 1991) of the Soviet Union, the war also emphasized the role of the United States as the world's single superpower at the beginning of the 21st century, its culture and technology spreading around the globe.